Best words. An anti-Trump group out with a new ad underscoring the GOP front-runner's frequent use of expletives. Will it move voters away from Trump?

Nuclear threat, North Korea saying it will launch what it calls a preemptive and offensive nuclear strike on U.S. and South Korean forces now engaged in war games. The U.S. saying it's taking the threat seriously. Is Kim Jong-un about to order a nuclear attack?

And quest for truth. Two years to the day since the disappearance of Malaysia Flight 370, CNN's Richard Quest is out with a comprehensive new book on the world's greatest aviation mystery. A newly discovered piece of debris now on its way to Australia for analysis, will it lead to the wreckage of the doomed plane?

We want to welcome our viewers in the United States and around the world. I'm Wolf Blitzer. You're in THE SITUATION ROOM.

ANNOUNCER: This is CNN breaking news.

BLITZER: Breaking political news tonight, just hours out ahead of the next round of presidential primaries and caucuses.

Former New York City Mayor Michael Bloomberg has just announced he will not join the race for the White House in part because his candidacy could lead to a Donald Trump victory. Bloomberg goes on to slam Trump's campaign, saying it's preying on people's prejudices and fears.

We're also following North Korea's disturbing threat to launch what it calls a preemptive and offensive nuclear strike against U.S. and South Korean troops. Kim Jong-un angered by joint military exercises under way right now in South Korea and furious at new United Nations sanctions in response to North Korea's ballistic missile test.

We're covering all of that, much more this hour, with our guests, our correspondents and expert analysts.

Let's begin with the breaking political news, Michael Bloomberg announcing he will not run for president for fear of helping Donald Trump win.

CNN's Sunlen Serfaty has details.

Sunlen, Bloomberg also very, very critical of Trump's campaign.

SUNLEN SERFATY, CNN NATIONAL CORRESPONDENT: That's right, Wolf. And in this article where he announces his decision which is entitled "The Risk I will Not Take," Bloomberg blasts Donald Trump, calling Trump's campaign the most divisive he can remember, one that preys on people's prejudices and fears.

(BEGIN VIDEOTAPE)

SERFATY (voice-over): After flirting with a potential White House run for months, former New York Mayor Michael Bloomberg today firmly said no, ruling out an independent bid for president.

In a column just published tonight on Bloomberg View, he writes -- quote -- "It's clear to me that if I entered the race, I could not win. I believe I could win a number of diverse states, but not enough to win the 270 Electoral College votes necessary to win the presidency."

SERFATY: This comes as Donald Trump and Ted Cruz are making the case that the Republican nominating fight is now looking like a two-man battle.

TRUMP: I would love to take on Ted one on one.

SERFATY: Both using their big weekend wins to pressure their rivals to reassess their campaigns.

SEN. TED CRUZ (R-TX), PRESIDENTIAL CANDIDATE: If you're not able to win primaries, if you're not amassing delegates to get the nominee, I think every candidate has to reflect, has to meet with their team and say do we have a path?

SERFATY: Cruz's potential path is getting a boost after banking crucial wins in Maine and Kansas, picking up more delegates this weekend than any other candidate.

CRUZ: We're now the only campaign that has beaten Donald Trump over and over and over again. Seven different times, we have beaten Donald Trump. The only way to win this election to beat Hillary Clinton is to run a strong principled conservative who stands with the people.

SERFATY: But the math and momentum are still on the front-runner's side, Trump with wins in Louisiana and Kentucky leading with 389 delegates, Cruz 302, Rubio after winning Puerto Rico at 149, and John Kasich far behind with just 37 delegates.

[18:05:01]

Trump, meanwhile, is hoping for another big Super Tuesday showing.

TRUMP: We're going to have, I think, a couple of good of ones tomorrow, I hope.

SERFATY: The big prize tomorrow night, delegate-rich Michigan, the polls there showing Trump leading by a large margin.

TRUMP: I have been to Michigan a lot. And I think we're going to do well there.

SERFATY: That as the candidates keep their eyes on some big prizes up for grabs on March 15, including Florida, where Rubio faces a do-or- die situation. Trump taunting his rival today.

TRUMP: I tell you what. That guy, he couldn't be elected dogcatcher in Florida.

SERFATY: And a blistering attack with this new ad set to hit the airwaves in the senator's home state.

NARRATOR: Another corrupt, all talk, no action politician.

SERFATY: Rubio is now barnstorming his home turf looking to keep his presidential hopes alive.

SEN. MARCO RUBIO (R-FL), PRESIDENTIAL CANDIDATE: I'm the only one left that can unite us, but I'm also the one left running that can grow it.

SERFATY: Outside groups opposing Trump are hoping to stop him from picking up a win in the Sunshine State by launching an assault on the airwaves, depicting what a Trump presidency might sound like and featuring ads with veterans to slam Trump's lack of military service.

SERFATY: And there's a new Florida poll out tonight from Monmouth University showing that Trump is leading. He's ahead of Rubio by eight point, ahead of Cruz by 21 points. Of course, Florida is a winner-take-all state, Wolf, 99 delegates at stake next Tuesday.

BLITZER: March 15, a huge day in this race for the White House. Sunlen, thank you very much.

The Rubio campaign looking closely and anxiously at all its options.

Tonight, our national correspondent, Jason Carroll, is at a Rubio rally in Tampa, Florida.

Jason, what is Marco Rubio saying about all of this?

JASON CARROLL, CNN NATIONAL CORRESPONDENT: Well, he just wrapped up his rally.

And when he opened it up to the audience, he started out by saying, well, it all comes down to Florida. And the audience erupted with applause because they know what's at stake here. In order for him to move forward, he must win Florida. Everyone here knows that. But despite that, despite that he's trailing in some of the polls, he says he's going to stay in this race.

(BEGIN VIDEO CLIP)

SEN. MARCO RUBIO (R-FL), PRESIDENTIAL CANDIDATE: I'm going to be on the ballot. We're going to win Florida. This is going to be very long process. You guys have never covered a campaign like this. This is unchartered territory. No one, not even Donald Trump is on track right now to have 1,237 delegates.

I mean, Donald Trump would literally have to win every -- half the delegates remaining between now and the end of this to be the nominee, and he's not on pace to do that.

(END VIDEO CLIP)

CARROLL: Well, the candidates are asking him to drop out, saying that he's not on track to win. Even some of his own advisers, Wolf, saying privately that perhaps it's time for him to step out of this race, not confident that he can take Florida, but Rubio, as you heard there, is very confident he can move forward.

They're going to stay on message. The strategy going forward, focus on the I-4 Corridor, those communities, like Orlando, like Tampa, where we are, South Florida, where he seems to be doing strong as well. They're also encouraged by early voting, Wolf, which seems to suggest that voters, according to what that campaign is saying, are leaning towards Rubio, rather than Trump -- Wolf.

BLITZER: Jason Carroll at that Rubio rally in Florida, thank you very much.

Once again, sources telling CNN special correspondent Jamie Gangel that the Rubio campaign is having serious internal debate about how to handle next week.

CNN's reporting that Marco Rubio himself is very bullish about his chances, wants to stay in, but some of his advisers -- some of his advisers -- suggesting he really can't win, should get out before the Florida primary, which is a week from tomorrow, March 15. Recent polls do show Rubio trailing Trump in Florida. Today, Trump launched an attack ad against Rubio.

Alex Conant is the communications director for Senator Rubio, who is with us as well.

Alex, thanks very much for joining us. Let's talk a little bit about what Jamie Gangel has been reporting,

what you're hearing, that Rubio himself very, very bullish. Wants to stay in this race. But some advisers maybe wondering if can't win in Florida, maybe it's best to get out before March 15.

She did not contact the campaign prior to coming on the show last hour in reporting that. It is absolutely 100 percent absolutely false. I think CNN is doing a disservice to voters by airing that sort of reporting without even checking with the campaign.

Her sources, whatever they are, have no idea what the internal operations of the campaign are because if she did, she would know that Marco feels confident about Florida.

Just a new poll today, a public poll today, showed Marco gaining from double digits down two weeks ago, single digits now. We're ahead in the early voting. We're going to be there for the next week. We know how to win in Florida. We're going to win in Florida. And it's going to be a new campaign -- a new day on the campaign the day after we win Florida.

BLITZER: Because some of her sources close to the campaign, inside the campaign -- not the senator himself, clearly not you, saying -- one of them saying he doesn't want to get killed in his home state, and maybe it would be smart, especially if he doesn't do well tomorrow, let's say, in Michigan and Mississippi, maybe to avoid some sort of humiliation, keep his credentials, it may be smart to get out even before March 15.

[18:10:18]

CONANT: Wolf, I have a lot of respect for you, but I'm going to ask you to stop reading that sort of fiction on air because it's not true at all. If Jamie had checked with the campaign, if Jamie had good sources in the campaign, she would have known that that is not true. That is fiction, and CNN should stop reporting it.

BLITZER: Well, let's talk a little bit about -- you don't know. There may be some private advisers, some senior advisers who aren't necessarily coordinating with the campaign, just speaking as sometimes they do candidly to a journalist, right?

CONANT: That's just not the case. That's just not the case, Wolf. I was sitting in a senior staff meeting planning out next week's schedule when I saw this report suddenly air, and I came racing across town --

BLITZER: I know, you came over here deliberately because you wanted to get your--

CONANT: Because CNN hadn't asked us for comment before that. I mean, CNN went to air with a report without asking a campaign for feedback. Who does that? How did that happen? How did that get to air without somebody asking the campaign for comment?

BLITZER: Well, I don't know. I assume Jamie Gangel and her producers and others did speak to someone in the campaign--

CONANT: She did not.

BLITZER: -- maybe they didn't speak to you, but maybe they spoke to others.

CONANT: I have not talked to anybody that she spoke to. And I was sitting in the room with the people that --

BLITZER: All right, so let's -- so let's get this straight. The senator, he's saying in the race irrespective of what happens tomorrow --

CONANT: Of course.

BLITZER: He's at least going to stay in the race until March 15 when Florida votes.

CONANT: Of course.

We feel very bullish about our chances in Florida. Look, we won Puerto Rico yesterday. There's a new poll today -- new poll out of Florida today showing that we have a lot of momentum in Florida. We feel good about the contest tomorrow. We're going to win more delegates on Tuesday. We're going to win delegates in D.C. on Saturday when D.C. has their convention. And then we're going to win the Florida primary.

Come next Wednesday, when you have me back on set next Wednesday, you're going to see Marco making huge gains in the delegates, and really being on the path to being the Republican nominee.

BLITZER: The other day, there was a poll that had him down by about 20 points, but now, this latest Monmouth poll that just came out today, Trump is at 38 percent in Florida, Rubio's at 30 percent. He's still behind, but he's narrowed that gap.

CONANT: Yes, exactly. We have momentum in Florida. We're going to win Florida. And if you look inside that poll, it shows that the people that already voted, the early voters are overwhelmingly in favor of Marco.

Look, we feel very good about the trajectory of the campaign. We're really looking forward to the debate in Miami on CNN on Thursday night. It's going to be a good moment for our campaign. And then we're going to--

BLITZER: So, I just want to be precise. You're the communications director for the campaign. Definitively, there's no way he's going to get out of this race before Florida?

CONANT: Look, Marco is -- definitively, there is no way -- not only is he not getting out of the race before Florida, he's not getting out of the race after Florida.

BLITZER: Even if he doesn't win in Florida?

CONANT: We're going to win Florida.

BLITZER: Well, let's say he doesn't win.

CONANT: Look, we're going to win Florida. But either way, Marco is committed to going to all 50 states in his pickup truck if he needs to be because we cannot et Donald Trump become the Republican -- become the nominee of the Republican Party. And the best way to stop Donald Trump is for all your viewers in Florida to go vote today, go vote early for Marco Rubio.

BLITZER: There is early voting in the state of Florida. But you know that Donald Trump says he should get out. Ted Cruz says he should get out--

CONANT: Well, of course. They're running against him.

BLITZER: They want a two-man race.

CONANT: I think they should get out.

BLITZER: They want Kasich to get out basically as well.

CONANT: Yes, well, I wish everyone would drop out except for Marco. That's not going to happen. Look, we have a four-person race. And that's the reality. It's going to be very competitive. Marco's going to win Florida.

And we're going to have -- we're going to be well on our way to securing the delegates we need to -- if not winning the nomination outright, winning it at the convention in Cleveland.

BLITZER: Trump is really going after Rubio, as you know. He's got a new ad that he put out today. Let me play a little clip from that and get your reaction.

CONANT: Thanks.

(BEGIN VIDEO CLIP)

NARRATOR: Rubio's been a total no-show in the U.S. Senate with the worst voting record of all. Marco Rubio, none other, corrupt, all talk, no action politician.

TRUMP: I'm Donald Trump, and I approve this message.

(END VIDEO CLIP)

BLITZER: All right. I will get your reaction.

CONANT: Well, two things. One, if Donald Trump was actually confident he was going to win Florida, he wouldn't be running that kind of ad with his own money on the air in Florida. Number two, those are the exact same attacks that Charlie Crist used against Rubio in 2010.

Floridians have heard that, those sorts of attacks. They know it's not true. They know Marco Rubio. They voted for him in 2010 even when Charlie Crist said that. Donald Trump is taking a page from Charlie Crist's playbook. It's not going to work any better for him than it did--

BLITZER: Is Senator Rubio going to devote almost all of his energies between now and March 15 to winning Florida?

CONANT: Yes, that's our priority.

I mean, obviously, we were in Idaho yesterday. We have campaigns on the ground in all of the states, but Florida obviously is our priority.

BLITZER: For example, Ohio, that's on March 15 also. Kasich is working hard in Ohio. Trump is working hard in Ohio --

CONANT: We have a great team on the ground in Ohio. Josh Mandel is our state chair there. He's fantastic. Has been with us from day one.

But the priority is Florida. There's 99 delegates at stake. When Marco wins that, that's a big step towards the nomination.

BLITZER: Because after March 15, it becomes winner takes all. So let's say you do win Florida. Where do you go from there? Is there a path to getting that magic number and capturing the Republican nomination?

CONANT: Yes, absolutely.

BLITZER: Walk us through that.

CONANT: Well, I can do -- you can go state by state.

But after Florida, then you have Utah, a state that we feel very good about. We have people like Mia Love and Jason Chaffetz have been doing great work for our campaign out there. Wisconsin, a state similar to Minnesota, the state that Marco won. And then states in the upper Northeast.

[18:15:17]

Look, the race is going to look different after March 15, in part because Marco is going to have money, we're going to have momentum, and the map works in our favor.

Ted Cruz has shown he's very good at winning rural, small caucuses, but there's only two caucuses left after tomorrow.

BLITZER: Who is the bigger threat to Marco Rubio's winning the Republican nomination, Donald Trump or Ted Cruz?

CONANT: I think they're different threats, I suppose. I mean, obviously Donald Trump is the front-runner right now. He has

the most delegates. I think Trump -- or excuse me -- Ted Cruz had a good week last week, but he's about to run out of good territory to win delegates in.

BLITZER: You see he's opening up offices throughout Florida right now, spending money there, getting involved in Florida. I don't think he necessarily thinks he can win in Florida, but he's trying to hurt Rubio's chances.

CONANT: Well, we'll see. I mean, some of those offices have proven to be phantom offices. They don't actually have staff in them. It's more for, you know, a media story, saying that he's competing there.

Look, if people want to stop Donald Trump in Florida, they'll go vote for Marco Rubio. We're seeing that happen already in the early voting. The poll that you just cited shows that Marco has the momentum on the ground in Florida. Our campaign is optimistic and hopeful about the future, which is why reports like you had last hour were so concerning and disappointing.

BLITZER: Well, I'm glad you came over and got your point of view on. And I'm glad we also pointed out that you're right. The polls have narrowed, 20 points just a few days ago, now only eight points. We'll see what happens.

Still plenty of time between now and March 15. So--

CONANT: Thanks, Wolf.

BLITZER: And once again, that was Jamie Gangel reporting. That's what -- she wasn't making it up. That's what she was hearing from sources close to the campaign, inside the campaign. But I'm glad we got your perspective.

CONANT: Well, let the record reflect, it's totally not true.

BLITZER: Yes. That's it. So, thank you very much for that, Alex Conant, the communications director for Marco Rubio's campaign.

And, by the way, the senator is always welcome here, whenever he has a chance. We've got satellites. We can do it remote. We can do it any way he wants to join us. He's always welcome to join us.

CONANT: Appreciate that very much.

BLITZER: Thank you very much, Alex. Thanks for coming in.

We will take a quick break. We're going to get reaction from the Trump campaign, a whole lot more.

We will be right back.

(COMMERCIAL BREAK)

[18:21:28]

BLITZER: Opponents of Donald Trump is stepping up their attacks on the Republican presidential front-runner tonight, including an ad highlighting Trump's use of expletives.

And we're back with one of Donald Trump's key supporters, the Tea Party leader Scottie Nell Hughes of the USA Radio Networks.

Scottie, thanks very much for joining us.

I want to get your immediate reaction to what we just heard from Alex Conant, the communications director for the Rubio campaign, insisting there's no way that Marco Rubio is going to drop out of this race for the Republican nomination before the March 15 primary in Florida. Your reaction?

SCOTTIE NELL HUGHES, USA RADIO NETWORKS: Well, Alex did a very good job doing his job, which was to strongly disagree and to strongly show some support that Marco Rubio is going to stay in this race.

Unfortunately, there's enough rumors out there that I always say, when you have a bunch of little sparks, there's usually probably a fire somewhere. There's something that is causing this.

The Rubio campaign themselves aren't not helping. If you go to their Web site, they only have events listed for Senator Rubio until tomorrow night. They haven't even extended him showing that he has got any other events planned.

Plus, to Alex's point that he made with you, Wolf, I would like to see a plan. He never clearly said, if Marco Rubio does not win Florida, will he be out the following day? You still have to have eight states as it stands, according to the bylaws of the Republican Party, to even be nominated for president at the convention in Cleveland.

There's not even a pathway or a state right now that Senator Rubio is trending to win. So, you know, you can sit there and throw out he's not getting out, he's not getting out, he's going to win, but you have to actually some substance to back it up. And, unfortunately, besides words, there was nothing else that Alex offered to sit there and prove against the rumors that Senator Rubio is getting out.

BLITZER: But, as you know, Scottie, in the most recent polls, he's narrowed the gap. Trump was ahead by about 20 points in Florida not that long ago. Now in the new Monmouth poll that came out today, he's only ahead by eight points, 38 percent to 30 percent.

And you heard Alex Conant, the communications director for Rubio, saying that they feel they have the momentum in their home state of Florida and they're going to win.

What do you say to that?

HUGHES: That always happens. Usually, these polls do tighten.

But when you look at the state of Florida right now, there's $10 million being spent down there against Mr. Trump. And it's not necessarily coming from Senator Rubio himself.

And when you have that much negative ads, I have to wonder, what are you trying to cover there? Maybe if they would spend that amount of dollar amount promoting Marco Rubio, instead of tearing down Mr. Trump, it would have a better traction.

But right now, when you talk to people in Florida, they say every other commercial is negative, negative, negative. At some point, they realize that actually, I think, starts to become counterproductive, as people get tired of it and they see that this is obviously an attack of the establishment, the exact thing that the American people right now are rebelling against.

BLITZER: Let me play an anti-Trump, an anti-Donald Trump ad that has just come out by a political action committee that clearly does not want Donald Trump to be the Republican presidential nominee. Listen to this ad.

(BEGIN VIDEO CLIP)

TRUMP: I went to an Ivy League school. I'm very highly educated. I know words and the best words. This is your (EXPLETIVE DELETED). He gets the nomination, they're going to sue his (EXPLETIVE DELETED). She said he's a (EXPLETIVE DELETED). We will beat the (EXPLETIVE DELETED) out of them. They're ripping the (EXPLETIVE DELETED) of the -- bull (EXPLETIVE DELETED). What the hell are we doing? You are not going to raise that (EXPLETIVE DELETED) price.

I have the best words. And you can tell them, go (EXPLETIVE DELETED) themselves.

NARRATOR: American Future Fund Political Action is responsible for the content of this advertising.

But what it shows right now is that he's definitely not a politician. In some cases, it might actually help him with some folks.

[18:25:00]

But here's the thing. When you listen to that ad right there, you hear the frustration, you hear the anger, which is the same thing that the majority of people right now when you talk to them feel about the establishment.

I wish at the end, instead of having that caption of the PAC, Wolf, that it would actually say the people that were paying for it, the actual donors. These are the same donors that have put the establishment time and time again and shoved them down throats. That ad right there I think will be counterproductive, because people

will see it for what it is, a total hit piece. In response, Mr. Trump has said, you know what? You guys attack me with dollars on the airwaves, I'm going to do the same thing I have always been doing. I'm going to go on Facebook. I'm going to go on Twitter. I'm going to use social media and I'm going to talk directly to you, the voters.

And if you go and read his Twitter feed right now, people will ask him questions and he's constantly responding back to them, something more than any other candidate is doing. That's how he's winning more than other candidates when they're spending three to four times than he is and also the money that's going against him.

BLITZER: Do you feel that Cruz, though -- he's won several contests in the last few days -- that there's a momentum on his part?

HUGHES: Well, there's definitely momentum on Senator Cruz's part. But the question is, where does it go?

Because you look at right now -- we mentioned earlier that there's one poll in Michigan right now that has Kasich actually beating Senator Cruz by one point. So they're neck and neck right now. And so right now, if I was going into tomorrow or going into Thursday and I was sitting there in the Cruz camp, I would be looking at Kasich and saying, you know what? I need to get Kasich out. He's the one that's the exact actual -- probably the opposite of Mr. Trump on a lot of things.

And that's probably the one that I would sit there saying, he's actually more of a threat probably than Marco or Cruz is.

BLITZER: Scottie Hughes, thanks very much for joining us.

HUGHES: Thank you, Wolf.

BLITZER: Just ahead, after big weekend wins, Donald Trump and Ted Cruz, they're urging Marco Rubio to get out of the race. What does it mean, though, if Michael Bloomberg is staying out of the race? Our experts are standing by.

(COMMERCIAL BREAK)

BLITZER: Breaking political news this hour. The former New York City mayor, Michael Bloomberg, just announcing he has decided not to join the race for the White House for fear his candidacy might help Donald Trump win.

Gloria, Bloomberg in this article, he just posted, releasing a statement criticizing both parties but especially harsh words for Donald Trump, saying this: "I have known Mr. Trump casually for many years, and we have always been on friendly terms. I even agreed to appear on 'The Apprentice' twice, but he's run the most divisive and demagogic presidential campaign I can remember, preying on people's prejudices and fears. Abraham Lincoln, the father of the Republican Party, appealed to our better angels. Trump appeals to our worst impulses."

Here's the question. He's not going to run himself, but will he get involved and try to influence this race in various other ways?

GLORIA BORGER, CNN CHIEF POLITICAL ANALYST: Look, I don't think he was not only anti-Trump, Wolf; he was anti-Ted Cruz. So -- and I think Michael Bloomberg probably doesn't have a lot of appeal with the base of the Republican Party right now. So even if he were to get involved and, say, push John Kasich or push Marco Rubio, I don't think it would have any influence at all.

I do think where he can -- he can get involved is in a general election. It seems to me from reading -- from reading his statement, if Kasich, if Cruz or Trump become the nominee, it's clear to me that Michael Bloomberg's going to be campaigning for the Democrat, if it's Hillary Clinton.

BLITZER: I assume he would.

Ron, let me read a little bit more about what Trump said. He said -- excuse me, what Bloomberg said. "We cannot make America great again by turning our backs on the values that made us the world's greatest nation in the first place. I love our country too much to play a role in electing a candidate who would weaken our unity and darken our future. And so I will not enter the race for president of the United States."

I always assumed he might enter the race for president of the United States if, let's say. Bernie Sanders were the Democratic nominee and Donald Trump were the Republican nominee. He would throw himself as an alternative to both.

But looking like Hillary Clinton is doing so well, that's presumably why he's not going to run.

RON BROWNSTEIN, CNN SENIOR POLITICAL ANALYST; You know, I was always skeptical, because Michael Bloomberg didn't make all those billions because he couldn't add. And in fact, I mean, the problem as a third- party candidate is, even if you win a lot of votes, given how polarized we are now, it's very hard to win many states. And that's the paradox. The same polarization that creates more room for a third-party candidate in theory makes it harder to win actual states. Ross Perot won a higher share of the popular vote than any third-party candidate since 1924 and didn't win a single state.

And his basic analysis, I think, is right, Wolf. I mean, today our politics cuts right more along the lines of culture than class. And as a social liberal, Michael Bloomberg would have drawn more votes in the end from the Democrats and probably made it easier for Donald Trump or whoever the Republican nominee is to win. And I think, if that was his concern, he made the right call. BLITZER: He said, basically, David Axelrod -- he said if he were to

run, he probably wouldn't be able -- third-party candidate probably wouldn't be able to get 270 electoral votes. He said, and as a result, David, it would go to the House of Representatives, where the Republicans are the majority; and either Cruz or Trump or someone on the Republican nominee would emerge as the president of the United States. You accept that analysis?

[18:35:14] DAVID AXELROD, Well, I actually think he's giving himself the benefit of the doubt that he would take some states. I'm not sure that he'd take any states.

Look, I agree with Ron. They've been looking at this for months. They've studied it, every aspect of it. They've had very smart people looking at this. There's no scenario here where he could play, and I don't even think he would even play that role.

He might take some more votes from the Democrats than from the Republicans. He might tilt a few states one way or the other. But by and large, I think this would be a bad investment. And as Ron said, he didn't get rich by making bad investments.

BORGER: Does it sound to you like he's for Hillary Clinton if she's the nominee?

BROWNSTEIN: Yes.

BORGER: Well, certainly. And the language about Trump was unsparing. I don't think he feels much better about Cruz, and they seem to be the leading alternatives, so yes.

BLITZER: What about, David, what if Bernie Sanders were to be the Democratic nominee, and Trump were to be the Republican nominee? Would Michael Bloomberg have second thoughts?

AXELROD: I think that he would spend a lot of time at his estate in Bermuda playing golf.

BLITZER: So he wouldn't--

AXELROD: Maybe ask -- maybe ask for asylum.

BLITZER: You don't think he would be considered. Go ahead, Ron. You want to weigh in?

BROWNSTEIN: I would say, there's an interesting convergence. Almost exactly at the same time that Mr. Bloomberg put out that statement Donald Trump put out a statement, criticize -- playing off of a census report on the level of legal immigrants and their children living in the country and underscoring something that hasn't been talked about very much.

Which was he also has called for a, quote, "pause" in the level of legal immigration, not just undocumented immigrants, deportation and the wall, but opposing continued legal immigration. Kind of really underscoring the Bloomberg message. As Trump portrays it, kind of the foreign-born as a threat to the economic prosperity, in some cases the physical security of native-born Americans.

I thought it was an interesting moment for those two things to come together. Trump doing something precisely at the moment Bloomberg stepped out that kind of underscored his point.

BLITZER: All right, guys. Stand by. There's more breaking political news we're following on this very dramatic race for the White House. We'll take a quick break. We'll be right back.

(COMMERCIAL BREAK)

[18:42:03] BLITZER: Republican presidential candidate Ted Cruz saying tonight -- and I'm quoting him now -- "momentum is surging our direction" after the most recent round of primaries and caucuses.

Ron Brownstein, Ted Cruz, he had a good weekend. He won Maine; he won Kansas. Two very different states. He also made it clear he doesn't want the nomination to be decided at a contested convention. Can he sell this right now effectively as a two-man race between himself and Trump?

BROWNSTEIN: I'd say not yet. I mean, he did have a good weekend. Maine was, I think, the most important winning a state outside his comfort zone.

But Ted Cruz has been a candidate from the beginning mostly dependent on evangelical rotors. And he's let a lot of states go by that Rick Santorum and Mike Huckabee won that he didn't win.

And now he's in a situation where there very few states left where evangelical voters are going to be a big piece of puzzle. Some of them in places you wouldn't expect: Michigan, Illinois, Florida, all around 40 percent. Ohio and Missouri around half the voters. So in the next two weeks, I think it's going to be very clear whether he can expand beyond his base among evangelicals and, in particular, compete for the none-evangelical voters which he's had trouble winning pretty much everywhere outside of Texas and those small caucus states of Maine and Alaska.

CAMEROTA: We do have Mississippi, Gloria, tomorrow. A lot of evangelical Republicans there.

BORGER: Over 80 percent evangelicals in Mississippi. And that -- you know, that is a big -- that is a big opportunity for Ted Cruz. And if he doesn't win Mississippi, then you know he really has a problem, because he's been splitting these evangelical voters with Donald Trump. So that is a real target for him tomorrow.

BLITZER: David, in the meantime, Kasich, John Kasich seems to be warming up to the possibility of some sort of contested convention, even acknowledging he's unlikely to win the nomination, get enough pledged votes without one. Can he really emerge as a consensus pick with a relatively small delegate count?

AXELROD: Well, let me just say if he doesn't embrace the notion of a contested convention, he's got no business in the race. I mean, that's the only scenario that's open to him yet. And it really is a very remote -- it's a very remote one.

You know, his hope is to do very well in Michigan tomorrow and to then win Ohio while the others fade away and that he emerges as the alternative to Donald Trump.

He does represent a wing of the party that is very distinct from the others. The problem is, it's just not a big enough wing. And as long as the -- Marco Rubio is in the race, that's where the establishment chips have gone.

It's a tough row to hoe for Kasich. He's run a great campaign, I think. I'm just not sure he's running in a party that exists.

BLITZER: The biggest campaign -- biggest state tomorrow, Michigan, a very important race. Here are the latest Monmouth University poll numbers, Gloria. Trump is at 36 percent; Cruz at 23 percent; Kasich at 21 percent; Rubio down at 13 percent. Trump wins Michigan tomorrow. That's another big bonanza for him.

BORGER: Well, and it's also -- it also is a signal of some problems for John Kasich. Because it's the same demographic as his home state of Ohio, which is a must, must, must-win for him, because it's got 30 percent Catholics, Wolf; 40 percent of the electorate is evangelical.

[18:45:16] A lot of blue collar voters. And Kasich's appeal would be with those Catholic blue collar voters.

So, if he can't do better than even a close second to Donald Trump, that may spell some difficulty for him because this should be very comfortable terrain.

BLITZER: Ron Brownstein, if Trump does win tomorrow in Michigan and does win this Mississippi, two very different states, what does that say to you?

RON BROWNSTEIN, CNN SENIOR POLITICAL ANALYST: Well, it says he's in a strong position. Look, the race is in a very precarious position, as we talked about. After Super Tuesday, a candidate had normal -- if a traditional candidate had won the states that Trump won, Massachusetts and Arkansas and Vermont and Alabama, you would see the party consolidating around him, both elected officials and voters.

That's not happening. He's a plurality front-runner. He still has a bigger piece that anyone else, but it is not significantly growing. He's still winning about one third of the vote and we're not seeing officials flock to him.

I agree with Gloria. Michigan is a real tip off. You look at what's coming up very soon after -- Illinois, Ohio, Missouri, soon after that Wisconsin. I think it's going to tell us whether any of the other candidates can build a broad enough coalition to overcome Trump's dominance of blue collar Republicans.

In that Monmouth poll today, 46 percent of non-college Republicans for Trump, double the number for anyone else. And it's not clear anyone else can consolidate the rest of the party enough. It's a familiar dynamic we've seen in other places, to overcome that significant one advantage for Donald Trump.

BLITZER: We'll have all-day coverage tomorrow, of course, of what's happening in these contests tomorrow in Michigan, Mississippi, Idaho, Hawaii. Stay with CNN for complete coverage.

Guys, don't go too far away. We have much more news coming up after this.

(COMMERCIAL BREAK)

[18:51:21] BLITZER: North Korea's threatening a nuclear strike against the United States and South Korean forces conducting joint military exercises right now. It comes amid high tension of missile ballistic tests by Kim Jong-un regime and new sanctions approved by the United Nations in response.

Our global affairs correspondent Elise Labott is working this story for us.

Elise, this threat, is the U.S. taking it seriously?

ELISE LABOTT, CNN GLOBAL AFFAIRS CORRESPONDENT: Well, Wolf, you know, these are real textbook threats from North Korea which launches fiery rhetoric every time the U.S. and South Korea begin their annual drills. But this year, they are the largest war games ever and they reflect U.S. fears about escalating tensions in the region.

(BEGIN VIDEOTAPE)

LABOTT (voice-over): Calling for a preemptive and offensive nuclear strike, Kim Jong-un is ordering attacks on the U.S. and South Korea as the two allies begin their largest ever military drills. The countries are preparing for attacks on North Korea's nuclear and weapons arsenals the event of a conflict, officials warned, could rival the last Korean War.

JOHN KIRBY, STATE DEPARTMENT SPOKESMAN: We have an obligation -- an obligation that is underscored and made all the more urgent on the peninsula by his own actions.

LABOTT: The fiery rhetoric from Pyongyang is typical during the annual exercises, which it views as a rehearsal for invasion, in which today Kim called a, quote, "beheading operation" aimed at removing his regime.

It comes just days after Kim ordered the country's nuclear weapons to be ready to fire at a moment's notice. The U.S. intel chief warns North Korea is moving closer to building to a nuclear-tipped missile, although it hasn't been tested.

JAMES CLAPPER, DIRECTOR OF NATIONAL INTELLIGENCE: It's also committed to developing a long range nuclear missile that's capable of posing a direct threat to the United States:

LABOTT: For the past two months, tensions between Kim and his enemies have reached what military commanders call an all-time high, ever since North Korea launched a long range missile into space and tested components believe to be related to a hydrogen bomb.

The U.S. military flexed its muscle in response, flying stealth jets over South Korea and just last week, the United Nations slapped the Kim regime with the toughest sanctions to date. Now, the defiant young leader is vowing revenge. He's already firing rockets into the sea and new commercial satellite images suggest he may be preparing for another rocket launch.

With no development talks on the horizon, U.S. officials are watching closely for new provocations as Kim seeks to project ultimate power before a historic conference of the Korean Workers Party in May.

VICTOR CHA, CENTER FOR STRATEGIC & INTERNATIONAL STUDIES: There will be some sort of action by the North, I'm pretty certain. We're probably going to see a protracted period of tension on the Korean peninsula at least through the early summer.

(END VIDEOTAPE)

LABOTT: And China also voiced concerns about the size of the military exercises, suggesting that the U.S. and South Korea's drills could provoke a response from the North. Today, Beijing issued a statement warning both sides to call on restraint and said it will never accept war and unrest on its doorstep, Wolf.

BLITZER: On another sensitive global issue, what are you hearing about the prime minister of Israel, Benjamin Netanyahu, declining an invitation to meet with President Obama?

LABOTT: Well, the White House tells us the prime minister was coming for the annual AIPAC conference, that annual meeting of this large pro-Israel lobby. They gave him a meeting on March 18th. It was on the president's schedule. They just read in the news reports that the prime minister cancelled his visit. What -- they didn't give any reason to the White House, and they didn't even tell him.

But what we understand from sources familiar with the president -- the prime minister's trip that not only the U.S. and Israel are in the middle of negotiations on a very sensitive strategic defense military aide agreement, that's not really finished yet.

[18:55:11] And so, the prime minister didn't want to go home empty handed.

It's in the middle of this crazy campaign season. A lot of the candidates will be addressing AIPAC. Some of them have asked for a meeting with the prime minister. And, you know, after getting him involved in U.S. politics when he spoke to Congress about that speech, I think he's a little loathe to get involved in domestic politics. So, maybe he's going to postpone that visit for a while.

BLITZER: Better to stay in Jerusalem at least for the time being.

All right. Elise, thanks very much. Meanwhile, a suspected piece of debris from missing Malaysian Airlines

Flight 370 is heading to Australia for analysis. Malaysian officials took custody of the plane part today in Mozambique, where it was discovered on a beach.

The mystery of the Boeing 777, which went missing exactly two years ago today is the subject of a brand-new very important book, "The Vanishing of Flight MH370." The author, CNN aviation correspondent Richard Quest, who has covered this story from day one, from the very beginning.

Richard, first of all -- congratulations on the new book.

RICHARD QUEST, CNN AVIATION CORRESPONDENT: Thank you.

BLITZER: Quickly, if this new piece that was found in Mozambique is indeed confirmed to be a part of MH370, do you think it can track the location of the plane?

QUEST: Not hugely. It will show them roughly where it was maybe, possibly. But if you look at the piece, what you're really looking for is any signs of tearing, seeing how it became disengaged from the aircraft. Once you've seen that, Wolf, you can get a picture of was it ripped off at high speed? Is it likely to have pulled off when it entered the water?

But you are clutching at straws to some extent. You normally need more than just one or two pieces to make definitive statements like that.

You know, I was just looking at the clock, Wolf, and it is two years pretty much to the minute since we got that statement from Malaysia Airlines saying that the plane had gone missing, the 777, 9M-MRO.

And in that two years, Wolf, there's an enormous number of speculation, amount of speculation, there's a huge amount of rumor and gossip, but the actual number of facts on the ground are still appallingly low. We don't know where the plane is definitively, and we certainly don't know what happened in the cockpit, whatever anybody says.

BLITZER: Yes, and it's hard to believe. I think it's fair to say the greatest aviation mystery of all time. An Australian official, as you know, says it's very likely the plane will be found in his words very soon. Do you believe that?

QUEST: That's Martin Dolan, the commissioner. He's been saying that pretty much from day one. And indeed, the Malaysian prime minister said it and the ministry of transport. It's part of the rubric they say. They are confident, very confident, highly confident because they've still got about 1/3 of the 46,000 square miles of the most probable area still to search.

The issue happens if after they've done that, they haven't found the plane. Firstly, could they have missed it? Is the integrity of the search, as close to 100 percent as you can get. If they're happy with that and they still haven't got the plane, then,

Wolf, you'll remember we're back to looking at the INMARSAT data. How far maybe off to one side or the other. What route did the plane take? Was there anybody at the controls?

We don't know. We won't know. And they've still got the find the black boxes.

BLITZER: One of the fascinating details you write about in your excellent new book "The Vanishing of Flight MH370" is you actually met with the co-pilot of the plane not long before it vanished. We're showing our viewers a picture.

QUEST: Two weeks beforehand, two and a half weeks beforehand. We were flying. It was from Hong Kong to Kuala Lumpur.

It was pure coincidence. You know, the conspiracy theorists have said constantly, oh, clearly, CNN knew, did. We obviously didn't. But we flew together. It was an engaging young 27-year-old pilot, engaged to be married.

And the issue, of course, is did the pilots do it, one or the other? Did they do it? In my book, I said I don't think they did. I'm prepared to be wrong. But at the moment I still believe you can't blame these pilots without more than a shred of evidence, a bit of gossip, and a lot of rumor.

BLITZER: So, right now, do you believe we're any closer than we were a year ago, a year and a half ago?

QUEST: No. No, we're not. Anybody who says we are closer, we may have some more theories, a bit more evidence, but frankly we're actually no closer to actually pinning this one way or the other on what happened to that plane.

BLITZER: Let's not forget there were 270 people on that plane, right?

QUEST: Absolutely. Never forget that, two years ago today.

BLITZER: All right. Richard Quest, congratulations on this new book "The Vanishing of Flight MH370." There's the book jacket right there.